The present disclosure relates generally to information handling systems, and more particularly to a circuit for providing a constant inrush current for an AC power supply unit which provides power to an information handling system.
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Irrespective of the form of the IHSs, or of any specific hardware and/or software components embodied therein, a power supply unit (PSU) is indispensable for IHS operation. Conventionally, PSUs are implemented as switched-mode power supplies (SMPSs) to provide greater power conversion efficiency (e.g., as compared to a linear power supply). However, SMPSs in particular suffer from large inrush currents. Inrush currents, which are large transient currents exceeding a normal operating current, occur when an SMPS is first energized (i.e., turned-on). Without proper protection, such inrush currents may overstress circuit and/or system components, create unwanted electromagnetic interference, or cause other types of circuit disturbances and/or failures. Conventional PSUs may include a power-factor correction (PFC) circuit (e.g., including a rectifier and boost converter) front-end, followed by a bulky electrolytic capacitor for energy storage, then another isolated DC-DC converter downstream to generate the voltage (e.g., 12V) for computing devices, as shown in FIG. 10. The electrolytic capacitor need to address both 120 Hz ripple and hold up time requirement, so its size is usually big. To limit inrush current to the electrolytic capacitor at turn-on (e.g., when an AC power source is connected to the PSU), a power resistor or a negative temperature coefficient (NTC) resistor is generally used in series with the line input or in series with the electrolytic capacitor. In steady state, the power resistor or NTC resistor is short-circuited by a relay or a metal-oxide-semiconductor field-effect transistor (MOSFET) connected in parallel to the power resistor or NTC resistor. However, power resistors and NTC resistors are very bulky, a necessity to satisfy pulse power requirements. In addition, conventional inrush current limiting circuits (e.g., based on power resistors or NTC resistors) may still result in currents transients that are not entirely controllable, and which may degrade the circuit and/or component lifetime (e.g., of a capacitor, a rectifier, a fuse, a breakers, etc.).
Accordingly, it would be desirable to provide an improved system for limiting and controlling inrush currents.